Exercise sharp vision

starting position

Hang the Far board on the wall and stand far enough away that you can still see the letters clearly. You also hold the near board in your hand at a distance where you can just barely see the letters clearly. Now alternately read a letter near and far. Do not change the board until you have recognized the letter perfectly clearly.

final position

Now alternately read a letter near and far. Do not change the board until you have recognized the letter perfectly clearly.
Variant: With eye patch / one-eyed.